Water heater and a method of preventing the water heater from empty boiling

ABSTRACT

A water heater, which includes a water pipe, a combustor, and a dry-boiling protector. The dry-boiling protector includes a first sensor, a second sensor, and a controller. The first sensor senses a resistance of water in the water pipe, and the second sensor senses a flow rate of the water in the water pipe. The controller is electrically connected to the first sensor and the second sensor to stop the combustor to heat water when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period, and a flow rate sensed by the second sensor is not zero.

The current application claims a foreign priority to the patent application of Taiwan No.

102137714 filed on Oct. 18, 2013.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a water heater, and more particularly to a water heater with a dry-boiling protector, and a method of preventing the water heater from boiling dry.

2. Description of Related Art

Typically, a conventional water heater includes a water pipe, a combustor, a flow sensor, and a controller. The water pipe has an end connected to a water supply, and the other end connected to a faucet. The combustor heats the water in the water pipe, and the flow sensor senses a flow rate of hot water in the water pipe. The flow sensor senses a flow rate of the water in the water pipe when the faucet is opened, and it will give a signal to the controller to start the combustor.

In some circumstances, such as the water company suspended water, there might be air in the water pipe. In such condition, the controller still starts the combustor when the faucet is opened. However, it only has air, instead of water. in the water pipe, and that would cause “dry-boiling”, which would damage the water pipe. Another problem of “dry-boiling” is that the over-heated pipe will vaporize the water after the air, and team will come out of the faucet suddenly after a short time the user opened the faucet, and sometime the user is hurt by the stem. Therefore, the conventional water is needed to be improved.

BRIEF SUMMARY OF THE INVENTION

In view of the above, the primary objective of the present invention is to provide a water heater with a dry-boiling protector and a method of preventing the water heater from boiling dry.

In order to achieve the objective of the present invention, a dry-boiling protector of a water heater includes a first sensor and a controller. The first sensor provided on a water pipe of the water heater to sense a resistance of a fluid in the water pipe; and the controller is electrically connected to the first sensor to stop the water heater to heat water when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.

The present invention further provides a water heater, which includes a water pipe, a combustor, a first sensor, and a controller. The first sensor provided on the water pipe of the water heater to sense a resistance of a fluid in the water pipe; and the controller is electrically connected to the first sensor to stop the combustor to heat the water pipe when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.

The present invention also provides a method of preventing the water heater from boiling dry. The method includes sensing a resistance of a fluid in the water pipe; and stopping heating the fluid when the resistance is higher than a critical resistance for a predetermined period.

Therefore, the dry-boiling protector of the present invention may prevent the water heater from boiling dry.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which

FIG. 1 is a sketch diagram of the water heater of a preferred embodiment of the present invention;

FIG. 2 is a sketch diagram of the water sensor of the preferred embodiment of the present invention;

FIG. 3 is a flow chart of the method of preventing dry-boiling of the preferred embodiment of the present invention; and

FIG. 4 is a sketch diagram of another water sensor of the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a water heater of the preferred embodiment of the present invention includes a water pipe 10, a combustor 20, a sensing unit 32, and a controller 34.

The water pipe 10 is a metal pipe, having an input section 12, a heat section 14, and an output section 16. Cold water enters the water pipe 10 via the input section 12, flows through the heat section 14 (to be heated), and then hot water will come out via the output section 16. A faucet 36 is connected to the output section 16 to turn on or off the hot water. The combustor 20 has a heat exchanger 22, a burner 24, a gas pipe 26, a gas valve 28, and an igniter 30. The heat exchanger 22 has a plurality of plates 222, and the water pipe 14 passes through the plates 222 and is in contact with the plates 222. The burner 24 is under the heat exchanger 22 and is connected to the gas pipe 26. The gas valve 28 is on the gas pipe 26 to control the gas in the gas pipe 26, including turning on, turning off, increasing and decreasing the gas to the burner 24. The igniter 30 is beside the burner 24 to light a fire, therefore the burner 24 may heat the water in the water pipe 10 through the heat exchanger 22.

The sensing unit 32 includes a cold water temperature sensor 322, a hot water temperature sensor 324, a flow sensor 326, and a water sensor 328. The cold water temperature sensor 322 is provided on the input section 12 to sense a temperature of the water therein, and the hot water temperature sensor 324 is provided on the output section 16 to sense a temperature of the water therein. Both the flow sensor 326 and the water sensor 328 are provided on the input section 12. The water sensor 328 is defined as a first sensor, and the flow sensor 326 is defined as a second sensor hereafter. The water sensor 328 senses a resistance of the water in the input section 12, and the flow sensor 326 senses a flow rate.

The controller 34 is electrically connected to the igniter 30, the gas valve 28, and the sensing unit 32 to control a gas flow to the burner 24 and the igniter 30 according to a cold water temperature, a hot water temperature, and a flow rate of water in the water pipe 10. The detail of controlling the hot water temperature is not the main feature of the present invention, so we do not describe the detail here.

As shown in FIG. 2, the water sensor 328 has two electrodes 328 a, both of which are electrically connected to the controller 34. The electrodes 328 a are separated from each other, and are suspended in the input section 12. An insulating member 328 b is provided between the electrodes 328 a and the water pipe 10 for secure of the electrodes 328 a and insulation. In an embodiment, an electricity with a constant current is provided to the electrodes 328 a, and a potential between the electrodes 328 a is measured, therefore, a resistance may be obtained. If the input section 12 is filled with water, the resistance should be a first resistance, which is water's resistance, and if the input section 12 is empty, the resistance should be a second resistance, which is air's resistance. The controller 34 is easy to determine that it's water or it's air in the water pipe 10 by the resistance sensed by the water sensor 328.

The flow sensor 326, the water sensor 328, and the controller 34 constitute a dry-boiling protector of the present invention, and the dry-boiling protector works with a method shown in FIG. 3.

The first resistance is affected by impurities in the water, and the second resistance is affected by moisture in the air. In order to correctly determine water or air in the input section 12, a critical resistance, which is higher than the first resistance, and is lower than the second resistance, is pre-stored in the controller 34. The controller 34 determines that it is water in the input section 12 when a resistance obtained by the water sensor 328 is lower than the critical resistance, and determines that it is air when a resistance obtained by the water sensor 328 is higher than the critical resistance.

In practice, there might be little water bubbles in the water pipe 10 only, and that is no harm for heating water. The controller 34 determines that it is air in the water pipe 10 only when the flow sensor 326 detects a water flow, which means the sensed flow rate is not zero, and a resistance obtained by the water sensor 328 is higher than the critical resistance for a predetermined period. On the contrary, the controller 34 determines that it is water in the water pipe 10 when the flow sensor 326 detects a water flow, and a resistance obtained by the water sensor 328 is lower than the critical resistance.

While a user is opening the faucet 36, the fluid (water or air) in the water pipe 10 begins to flow, and at the same time, the flow sensor 326 and the water sensor 328 start to work. If the controller 34 determines air in the water pipe 10 (the flow sensor 326 detects a water flow, and the water sensor 328 detects a resistance higher than the critical resistance), the controller 34 closes the gas valve 28 to cut off the gas and idles the igniter 30.

When the burner 24 is burning gas to heat the water in the water pipe, which means that the water heater is working, and the controller 34 determines air in the water pipe 10, the controller 34 closes the gas valve 28 to cut off the gas. It may prevent the water heater from boiling dry to protect the heat exchanger 22 and water pipe 10 and to avoid steam coming out of the faucet 36.

FIG. 4 shows another water sensor 40, which has an electrode 402 only. The electrode 402 is suspended in the input section 12. The water pipe 10 is electrically connected to the controller 34 to be the other electrode of the water sensor 40. A resistance between the electrode 402 and the water pipe 10 can be measured to determine water or air in the input section 12.

In an embodiment, water or air is determined by the water sensor 328 only without the flow sensor. The controller 34 determines air in the water pipe 10 when the resistance obtained by the water sensor 328 is higher than the critical resistance for a predetermined period, and then the controller 34 cuts off gas.

In conclusion, the present invention provides the water sensor to sense a resistance which may help the controller to determine it is water or air in the water pipe, and the controller will cut off gas while air is detected to prevent the water heater from boiling dry. The dry-boiling protector of the present invention also may be allied in an electric water heater as well.

It must be pointed out that the embodiments described above are only some preferred embodiments of the present invention. All equivalent structures which employ the concepts disclosed in this specification and the appended claims should fall within the scope of the present invention. 

What is claimed is:
 1. A dry-boiling protector of a water heater, which the water heater has a water pipe, the dry-boiling protector comprising: a first sensor provided on the water pipe to sense a resistance of a fluid in the water pipe; and a controller, which is electrically connected to the first sensor, stopping the water heater to heat water when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.
 2. The dry-boiling protector of the water heater of claim 1, further comprising a second sensor provided on the water heater to sense a flow rate of the fluid in the water pipe, wherein the controller stops the water heater to heat water when a flow rate sensed by the second sensor is not zero, and a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.
 3. The dry-boiling protector of the water heater of claim 2, wherein the water pipe has an input section where cold water enters the water pipe, and both the first sensor and the second sensor are provided on the input section.
 4. The dry-boiling protector of the water heater of claim 1, wherein the first sensor has two electrodes, both of which are electrically connected to the controller and are suspended in the water pipe to sense a resistance between the electrodes.
 5. The dry-boiling protector of the water heater of claim 1, wherein the first sensor has an electrodes, which is electrically connected to the controller and is suspended in the water pipe, and the water pipe is a metal pipe electrically connected to the controller to sense a resistance between the electrode and the water pipe.
 6. The dry-boiling protector of the water heater of claim 1, wherein the water heater further has a gas pipe, a burner, and a gas valve; the gas pipe supplies gas to the burner; the gas valve, which is on the gas pipe, is electrically connected to the controller to cut off the gas in the gas pipe by a command of the controller.
 7. A water heater, comprising: a water pipe; a combustor for heating the water pipe; a first sensor provided on the water pipe to sense a resistance of a fluid in the water pipe; and a controller, which is electrically connected to the first sensor, stopping the combustor when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.
 8. The water heater of claim 7, further comprising a second sensor provided on the water heater to sense a flow rate of the fluid in the water pipe, wherein the controller stops the combustor when a flow rate sensed by the second sensor is not zero, and a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.
 9. The water heater of claim 8, wherein the water pipe has an input section and a heat section connected to the input section; cold water enters the water pipe via the input section; the first sensor and the second sensor are provided on the input section; and the combustor heats the heat section.
 10. The water heater of claim 7, wherein the combustor has a gas pipe, a burner, and a gas valve; the gas pipe supplies gas to the burner; the gas valve, which is on the gas pipe, is electrically connected to the controller to cut off the gas in the gas pipe by a command of the controller.
 11. The water heater of claim 7, wherein the first sensor has two electrodes, both of which are electrically connected to the controller and are suspended in the water pipe to sense a resistance between the electrodes.
 12. The water heater of claim 7, wherein the first sensor has an electrodes, which is electrically connected to the controller and is suspended in the water pipe, and the water pipe is a metal pipe electrically connected to the controller to sense a resistance between the electrode and the water pipe.
 13. A method of preventing a water heater from boiling dry, wherein the water heater has a water pipe, the method comprising the steps of: sensing a resistance of a fluid in the water pipe; and stopping heating the fluid when the resistance is higher than a critical resistance for a predetermined period.
 14. The method of claim 13, further comprising the step of sensing a flow rate of the fluid in the water pipe, wherein the step of stopping heating the fluid is performed when the flow rate is not zero, and the resistance is higher than a critical resistance for a predetermined period.
 15. The method of claim 14, wherein the water pipe has an input section where cold water enters the water pipe; and the resistance and the flow rate are sensed in the input section.
 16. The light acupuncture module of claim 13, wherein the water heater further includes a combustor, which burns gas to heat the water pipe; and the step of stopping heating the fluid is cutting off the gas to the combustor. 